1. Field of the Invention (Technical Field)
The present invention relates to the potential therapeutic use of the naturally occurring biologic tri-peptide pyroglutamyl-glutamyl-prolyl amide (xe2x80x9cEEPxe2x80x9d), and any and all peptide and protein analogues thereof. Included in the invention are the class of tri-peptides with NH2-terminal pyroglutamyl- and COOH-terminal prolyl amide, but with variable internal amino acids; that is, where the internal glutamate has been substituted for some other internal amino acid or the analogues thereof with the exception of histidine and its analogues. The invention includes any chemical derivatives of EEP which elicit any of the physiological or therapeutic effects of EEP.
2. Background Art
Pyroglutamyl-glutamyl-prolyl amide (xe2x80x9cEEPxe2x80x9d) is a naturally occurring biologic tri-peptide found in the blood and internal organs of animals, including humans. EEP is synthesized naturally in the brain, and possibly other organs from the cleavage of a larger protein or peptide. However, this precursor protein is different from the well-characterized precursor of thyrotropin-releasing hormone xe2x80x9cTRHxe2x80x9d). The TRH precursor, prepro-TRH, has been fully sequenced, and the EEP sequence is not present within prepro-TRH. Similar to TRH, the EEP peptidergic system occurs within the limbic system neurons in the central nervous system (xe2x80x9cCNSxe2x80x9d), and the amounts of each increase following seizures. See, Lloyd et al., Society for Neuroscience Abstracts, Vol. 23(Part 2), p.1661, 1997; Pekary et al., Society for Neuroscience Abstracts, Vol. 23(Part 2), p.2377, 1997; Sattin et al., Annals NY Academy of Science, Vol. 739, pp. 135-153, 1997, and Pekary et al., xe2x80x9cElectroconvulsive seizures increase levels of pGlu-Glu-Pro-NH2. (EEP) in rat brainxe2x80x9d, Peptides, 1999, the teachings of which are hereby incorporated by reference.
TRH has been shown to produce marked improvement in neurological and neuromuscular functions associated with both lower and upper neurons. See, Engle, U.S. Pat. No. 4,608,365. For example, when given to patients with amyotrophic lateral sclerosis, TRH produced a marked improvement of functions of both lower and upper neurons. However, because of the instability of TRH in the blood, the beneficial effects last from only one to 24 hours and high doses are required (0.71 mg/kg of body weight, once or twice per day) depending upon the patient. Accordingly, TRH is generally administered by continuous intravenous infusions in high doses, and only in exceptional cases is intramuscular or peroral administration considered. See, Geirtz et al., U.S. Pat. No. 4,906,614. Attempts have been made to synthesize chemical analogues of the TRH molecule that have the biological properties of TRH but which are stable toward metabolizing enzymes. For example, O""Leary et.al, reports in Journal of Neurochemistry, Vol. 65, No. 3, pp. 953-63 that a methyl substituted histidyl analogue of TRH is less prone to metabolic degradation. Other examples include the report of Giertz who substituted the C-terminus of TRH, i.e., pyroglutamyl moiety, for a cyclic organic moiety, and Spattola et al., U.S. Pat. No. 5,244,884 who reported a thionated analogue of TRH whereby at least one of the four carbonyl oxygens was substituted with sulfur. One distinguishing feature of all these TRH analogues, in relation to the present invention, is that they all bind to TRH receptor sites within the brain. In contrast, EEP although exhibiting TRH-like physiological effects, does not bind with TRH-receptors. The present invention however is not limited by this physiological relationship, since some of the chemical analogues of EEP may interact with TRH receptors to some extent.
EEP differs from TRH in that the middle amino acid is glutamate instead of histidine. This structural difference is significant because the absence of the histidine residue in the former precludes digestion of the tri-peptide by pyroglutamate aminopeptidase 11 (xe2x80x9cPAP IIxe2x80x9d). PAP II is known to hydrolyze only tri-peptides containing N-terminal pyroglutamate and with histidine in the penultimate position.
Like TRH, EEP is shown to be an effective antidepressant in the highly predictive rat Forced-swim test. However, because EEP has a longer half-life under physiological conditions, its potency in the rat Forced-swim test might be as high as forty fold greater than that of TRH. In addition, EEP occurs naturally in the blood as well as in the brain, and more importantly it is not significantly metabolically degraded in the blood. Thus, in contrast to the recent attempts to utilize TRH to treat depression, treatment with EEP, in accordance with the present invention, can be applied as a practical alternative. For example, EEP can be administered intravenously, subcutaneously or orally, while TRH requires invasive injection into the spinal fluid. See, Callahan et al., Biological Psychiatry, Vol. 41, pp.263-272, 1997, Marangell et al., in Archives of General Psychiatry, Vol. 54, pp. 214-222, 1997. In the reports by Callahan et al., and Marangell et al., patients with depression responded with improvement to 500 micrograms (0.5 milligram) TRH.
The present invention is a drug for treatment of neurological and neurobehavioral disorders of mammals, including humans. The drug comprises a tri-peptide comprised of an N-terminal pyroglutamyl moiety, a C-terminal prolyl amide moiety, and an internal amino acid or analogue thereof.
In one embodiment, the internal amino acid comprises an amino acid other than histidine or its analogues. In another embodiment, the amino acid(s) comprises glutamate or phenylalanine.
The present invention is also a method of treating neurological and neurobehavioral disorders of mammals by administering the tri-peptide to a mammal.
The invention also includes methods of administering the tri-peptide to a mammal that result in improvements in the following disorders: neuromuscular weakness, spinal cord trauma, spasticity, schizophrenia, dementias, Alzheimer""s, somatization disorders, psychosomatic disorders, functional bowel disorders, epileptic disorders, sleep disorders, and loss of motoric or cognitive functions resulting from spinal cord or brain stem injuries.
The invention includes the following modes of administration: oral, parenteral, intranasal, transcutaneous, and rectal.
The invention also includes a method to detect and assay the tri-peptide, which includes subtracting the amount of tri-peptide containing an internal histidine or histidine analogue from the total amount of TRH-like tri-peptide present in the blood or tissue sample.
The use of the present invention is for the treatment of various neurological and neurobehavioral disorders in humans and any form of animal life for which the licensed health practitioner or veterinarian deems such treatment appropriate.
Primary object of the present invention is to provide pharmaceutical compositions of the present invention for use in the above-mentioned treatments.
A primary advantage of the present invention is the relatively high metabolic stability of EEP in the blood.
Another advantage of the present invention is that it maintains high levels of efficacy under different modes of administration, and may be combined with many different treatments without adverse effect.
Another major advantage of the present invention is the unprecedented rapid onset of the therapeutic effect, within one day, or within hours, in contrast with all established previous treatments which (e.g. in the case of depression) require weeks.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.